TABLE 2

Reported activities of cannabinoid receptor ligands at recombinant GPR55 in various assays

The structures of all compounds listed are shown in Figures 1–5.

Ligand	[³⁵S]GTPγS Binding	ERK1/2 Phosphorylation	[Ca²⁺]_i Mobilization	β-Arrestin	GPR55 Internalization	RhoA Activation
LPI	EC₅₀ = 1 μM^{^a}	EC₅₀ = 200 nM^{^a}	30 nM^{^a}	EC₅₀ = 3.6 μM^{^b}	3 μM^{^c}	1 μM^{^d,^e}
		1 μM^{^d,^f}	3 μM^{^g,^h}	EC₅₀ = 1.2 μM^{^c}
			3 μM^{^c}	EC₅₀ = 49 nM^ⁱ
			10 μM^{^j}
Anandamide	EC₅₀ = 18 nM^{^k}	10 μM^{^j}	5 μM^{^g}	Very weak agonist^{^b}	N.E.^{^c}	1 μM^{^k}
			EC₅₀ = 7.3 μM^{^j}	N.E.^{^c}
2-AG	EC₅₀ = 3 nM^{^k}	N.E.^{^a,^c}	N.E.^{^h,ⁱ}	N.E.^{^c}	N.E.^{^c}	N.T.
Δ⁹-THC	EC₅₀ = 8 nM^{^k}	N.E.^{^a}	5 μM^{^g,^h}	N.E.^{^c}	N.E.^{^c}	5 μM^{^g}
Cannabidiol	IC₅₀ = 350 nM^{^k}	1 μM antagonist^{^d}	N.E.^{^g}	N.E.^{^c}	N.E.^{^c}	1–10 μM antagonist^{^d,^k}
Abn-CBD	EC₅₀ = 2.5 μM^{^k}	N.E.^{^a}	N.E.^{^g}	N.E.^{^b,^c}	N.T.	N.T.
O-1602	EC₅₀ = 13 nM^{^k}	1 μM^{^d}	10 μM^{^j}	N.E.^{^c}	N.T.	1 μM^{^d,^e,^f}
	EC₅₀ = 2.5 nM^{^l}
CP55940	EC₅₀ =5 nM^{^k}	10 μM antagonist^{^c}	10 μM antagonist^ⁱ	K_i ∼200 nM^{^c}	K_i ∼200 nM^{^c}	N.T.
Rimonabant	N.T.	N.E.^{^a}	1–2 μM antagonist^{^g,^h,^j}	EC₅₀ = 9.3 μM^{^b}	30 μM^{^c}	N.T.
				EC₅₀ = 3.9 μM^{^c}
AM251	EC₅₀ =39 nM^{^k}	N.E.^{^a}	N.T.	3 μM^{^b}	30 μM^{^c}	N.T.
				9.6 μM^{^c}
AM281	EC₅₀ >30 μM^{^k}	N.T.	N.T.	N.E.^{^c}	N.E.^{^c}	N.T.

N.E., no effect; N.T., not tested.
↵a Oka et al. (2007): hGPR55 stably transfected in HEK293 cells with a tetracycline-inducible promoter.
↵b Yin et al. (2009): hGPR55 transiently transfected in HEK293 cells.
↵c Kapur et al. (2009): hGPR55E stably transfected in HEK293 cells (β-arrestin assay) or U2OS cells (β-arrestin and GPR55 internalization assays).
↵d Whyte et al. (2009): human osteoclast primary cultures.
↵e Whyte et al. (2009): mouse osteoclast primary cultures.
↵f Pietr et al. (2009): BV-2 (mouse microglial cell line).
↵g Lauckner et al. (2008): hGPR55 transiently transfected in HEK293 cells.
↵h Lauckner et al. (2008): mouse DRG primary cultures.
↵i Henstridge et al. (2009): hGPR55 stably transfected in HEK293 cells.
↵j Waldeck-Weiermair et al. (2008): EA.hy926 (human umbilical vein derived endothelial cell line).
↵k Ryberg et al. (2007): hGPR55 transiently transfected in HEK293s cells.
↵l Johns et al. (2007): hGPR55 transiently transfected in HEK293T cells.